MySQL觸發(fā)器的使用

關(guān)鍵字: MySQL 觸發(fā)器 1、創(chuàng)建觸發(fā)器:
語(yǔ)法:

CREATE TRIGGER trigger_name trigger_time trigger_event ON tbl_name   
FOR EACH ROW   
BEGIN   
trigger_stmt   
-
 

END；  

CREATE TRIGGER trigger_name trigger_time trigger_event ON tbl_name
FOR EACH ROW
BEGIN
 trigger_stmt
END；
例子
CREATE TRIGGER SetUserHome after insert ON users   
FOR EACH ROW   
BEGIN   
update `users` set homeLocationX = 128,
homeLocationY=128, homeLocationZ=30
where uuid = NEW.uuid
END 

以上的例子是錯(cuò)誤的， 讓本表進(jìn)行觸發(fā)時(shí)進(jìn)行更新會(huì)讓程序進(jìn)入死循環(huán)。

系統(tǒng)會(huì)報(bào)這樣的錯(cuò)誤：it is already used by statement which invoked this stored function/trigger.

應(yīng)該改成以下語(yǔ)句：

CREATE TRIGGER SetUserHome before insert ON users   
FOR EACH ROW   
BEGIN   
set New.homeLocationX = 128;
set New.homeLocationY = 128;
set New.homeLocationZ=30;
END 

大寫的為關(guān)鍵字
trigger_name:觸發(fā)器的名字，我常用的命名規(guī)則t_name_tableName_(b|a)(i|u|d),t:觸發(fā)器標(biāo)識(shí)，name:英文名，tableName:表名，b(BEFORE):標(biāo)識(shí)是觸發(fā)事件之前，a(AFTER):標(biāo)識(shí)觸發(fā)事件之后,i(insert):標(biāo)識(shí)insert事件，u(update):標(biāo)識(shí)update事件，d(delete):標(biāo)識(shí)delete事件;
trigger_time:觸發(fā)時(shí)間(BEFORE或AFTER)
trigger_event:事件名(insert或update或delete)
tbl_name:表名(必須是永久性表)
trigger_stmt：執(zhí)行語(yǔ)句(可以是復(fù)合語(yǔ)名)，使用別名OLD和NEW，能夠引用與觸發(fā)程序相關(guān)的表中的列。
2、刪除解發(fā)器
語(yǔ)法：
DROP TRIGGER [schema_name.]trigger_name；
注意：以上操作均需SUPER權(quán)限
示例：

DROP TRIGGER t_wiley_hotelComment_bu;   
delimiter //   
CREATE TRIGGER t_wiley_hotelComment_bu BEFORE UPDATE ON hotel_comment   
FOR EACH ROW   
BEGIN   
     IF OLD.ispass=0 && NEW.ispass=1 THEN   
        UPDATE hotel_info SET sumcomment=sumcomment+1,sumconsume=sumconsume+NEW.consume,sumservice=sumservice+NEW.service, sumroom=sumroom+NEW.room,sumentiron=sumentiron+NEW.entironment,total=total+(NEW.service+NEW.room+NEW.entironment) WHERE hotel_id=NEW.hotel_id;   
   ELSEIF OLD.ispass=1 && NEW.ispass=0 THEN   
      UPDATE hotel_info SET sumcomment=sumcomment-1,sumconsume=sumconsume-NEW.consume,sumservice=sumservice-NEW.service, sumroom=sumroom-NEW.room,sumentiron=sumentiron-NEW.entironment,total=total-(NEW.service+NEW.room+NEW.entironment) WHERE hotel_id=NEW.hotel_id;   
   END IF;   
END;//   
delimiter ; 

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